Wow, 20-year-old Marlins phenom Jose Fernandez was impressive against the Mets yesterday in his major-league debut.

So when is he getting traded?

That's the problem for Miami fans. Why get excited about a top-notch prospect when his prime years might be spent somewhere else?

The Mets? They displayed a different problem Sunday, one that could be equally vexing to their fans: absence of boldness.

When the Marlins needed an extra starter because of spring training injuries, they decided to roll the dice with Fernandez, who had never pitched above A-ball.

And, boy, did Fernandez dazzle. He retired the first 10 Mets, striking out five, and went on to allow one run, three hits and a walk with eight strikeouts in five innings. He was robbed of his first major-league win when the Mets rallied for two runs in the ninth for a 4-3 victory.

When the Mets needed an extra starter Sunday because of spring training injuries, they called on journeyman Aaron Laffey, who turns 28 on April 15. Not Zack Wheeler, the 22-year-old who started the season with Triple-A Las Vegas.

Wouldn't it have been thrilling to see the Mets' stud match up with Fernandez? Instead, the Mets sent out a soft-tossing lefty with a career record of 25-29. Another placeholder on a team filled with them. Laffey gave up 10 hits and three runs in 4 1/3 innings.

The Marlins say their decision was based solely on the belief that Fernandez is ready for the big leagues. After Sunday, when he showed a high-90s fastball and tight, late-breaking curve, it would be hard to dispute that.

The Marlins also could be accused of trying to excite their dispirited fan base, which is likely to stay away in droves when Miami opens its home season Tuesday. (That tends to happen when a 1-year-old stadium with a centerfield sculpture that looks like Picasso threw up becomes a major financial boondoggle just as the owner trades most of his best players away in a salary dump.)

Fernandez's backstory is as good as his stuff. Born in Cuba, he attempted to escape several times. After one of those tries, he was jailed.

The successful attempt came in 2008, but only after he rescued his mother from the Gulf of Mexico when she fell out of their boat, according to the South Florida Sun Sentinel.

"I've been in jail. I've been shot at. I've been in the water," Fernandez said Saturday. "I'm not scared to face David Wright. What can he do?"

Fernandez eventually settled in Tampa and went to high school there. He was the Marlins' first-round pick in 2011. His family was at Citi Field Sunday and could be heard squealing throughout his five innings.

The Mets' story with Wheeler is less dramatic. They never considered him for the majors, not early in spring training and not when Johan Santana and Shaun Marcum went down with injuries.

Wheeler's just not ready, they say, even though his stuff wowed everyone in Port St. Lucie. It's the same approach that led to a midseason promotion for Matt Harvey last year. Given that Harvey has been outstanding after reaching the majors, you could say the Mets made the right call.

Or . . . maybe Harvey would have starred in the majors earlier than late July.

Similarly, perhaps Wheeler -- who went only 3 1/3 innings in his first start for Las Vegas -- would harness the adrenaline of facing big-league hitters and blow them away with his 98-mph fastball.

You know this: If Sandy Alderson had been running the Mets in 1984, a 19-year-old named Dwight Gooden would not have made 31 big-league starts, won 17 games and struck out 276 batters.

Instead, the 1984 version of Aaron Laffey would have been pitching for the Mets, and 1986 might have looked a little different, too.